This invention relates to sewing machines and, more particularly, to an improved actuator for use in sewing machines utilizing stitch pattern signal responsive actuators for positioning the needle and/or the work feeding mechanism between successive stitches of a predetermined pattern.
In recent years, so called "electronic" sewing machines have gained in popularity and have met with commercial success in both industrial and domestic applications. These electronic sewing machines typically include a memory unit for storing in digital form information to control both the needle positioning mechanism and the work feeding mechanism to automatically produce a desired pattern. Signals generated from the stored information are applied to signal responsive actuators for selectively positioning the needle and the work feeding mechanism. These actuators may be of either the analog or the digital type. An analog actuator is responsive to an analog signal for positioning its associated mechanism at a point along a continuum between two extreme positions. The present invention is concerned with digital actuators wherein the actuator responds to digital input signals to position its associated mechanism at a selected one of a plurality of incrementally displaced discrete points between two extreme positions.
Digital actuators, per se, are well known. For example, both linear motors and stepping motors have been utilized in the prior art as actuators to position the needle bar and/or the work feeding mechanism in a sewing machine in response to stitch pattern signals stored in and retrieved from a memory unit. However, both of these types of actuators require some form of signal conversion from the digitally stored information to a signal usable as an input to the actuator itself. Thus, the linear motor requires a digital to analog converter to convert a digital input signal to an analog voltage level and the stepping motor actuator requires signal processing to provide appropriate signals for positioning the stepping motor. Such signal conversion requires circuitry which adds to the cost of the sewing machine.
It is therefore an object of the present invention to provide an actuator directly responsive to digital input signals.
Typically, the prior art actuators are directly coupled, through some intermediate linkage, to the controlled mechanism. This requires that the actuator have sufficient power to move both the intermediate linkage and the controlled mechanism.
It is therefore another object of this invention to provide an arrangement whereby the actuator mechanism may be of reduced size and have reduced power requirements.